[merraksh]

The Therac-25's software program, relatively crude by today's standards, probably contained 101000 lines of code. At one error for every 500 lines, that works out to the possibility of twenty errors.

I'd say 200, not twenty.

[pathdependent]

I think the article was OCR'd. There were a few other mistakes that were clearly misinterpreted characters. I think the 1 in the thousands place is actually a comma on the source.

[merraksh]

Good point. There are many hints that article was OCR'd, for instance an ".4ECL" instead of "AECL".